The present invention relates to apparatus for producing a plasma source of high-intensity radiation in the X-ray region. More particularly, the invention pertains to a so-called "plasma-focus" device, comprising spaced inner and outer electrodes which extend from a closed supporting (or upstream) end to define a discharge space which is gas-filled and open to the other (or downstream) end, there being an annular insulator surrounding the inner electrode and extending from the closed end for a fraction of the extent of overlap of the electrodes, and there being provision for momentarily supplying pulses of stored energy to the closed ends of the electrodes.
In these devices, with each supplied pulse of stored energy, ionization processes occur in the gas of the discharge space, leading to the production of a thin plasma layer which moves with great speed toward the open end of the discharge space. After reaching this open end, the plasma is compressed by magnetic forces onto the axis of the inner electrode. Such compression of the plasma occurs that one speaks of a plasma focus here. This plasma focus is of approximately cylindrical shape, with diameters of 100 to 300 .mu.m. X-radiation, inter alia, is produced in the plasma focus.
In known devices, the ionization processes at the closed end of the discharge space develop in uncontrolled manner, with resulting formation of individual spark channels, so-called "filaments". The resultant plasma layer is, therefore, not homogeneous but consists of a plurality of such filaments. Each of these filaments is surrounded by a magnetic field, and the magnetic fields around these filaments prevent maximum compression of plasma in the focus. The plasma focus thus has a focus diameter that is no longer reducible and, in particular, differs from discharge to discharge, i.e., the focus is not reproducible.
Due to the uncontrolled development of ionization processes in the gas space, the distribution of resultant filaments is not reproducible. The location of the resultant plasma focus is thus subject to certain variations.
Therefore, since neither the position nor the diameter of the plasma focus is reproducible in the known devices, such a focus cannot be used, for example, as a defined source of X-rays in X-ray optical instruments.